Jimmy and Jay sing their version of the classic duet Tonight from the Broadway musical West Side Story

US network NBC has announced its long-rumoured switch in late night, replacing host Jay Leno at The Tonight Show with Jimmy Fallon and moving the iconic franchise back to New York.

Saturday Night Live producer Lorne Michaels will take over as producer of the new Tonight Show.

Fallon's replacement at the 12:35am show Late Night was not named, although Seth Meyers of SNL is considered a strong candidate.

The move had been widely reported but not confirmed by the network until now. NBC reportedly just wrapped up negotiations with Fallon on a contract extension.

Steve Burke, chief executive officer of NBC Universal, said the network is purposefully making the move when Leno is still at the top of the ratings, just as when Leno replaced legendary host Johnny Carson at The Tonight Show.

"Jimmy Fallon is a unique talent and this is his time," Mr Burke said.

Fallon will take over in conjunction with NBC's coverage of next year's Winter Olympic games. NBC hopes for a big audience - much larger than what it gets in prime time now - to promote the handover.

Jay Leno, left, has confirmed that he will step down as host of theTonight Show next year, making way for Jimmy Fallon to take over behind the desk. Picture: Getty

NBC is worried that rival network ABC's Jimmy Kimmel will establish himself as a go-to late night performer for a younger generation if the network didn't move swiftly to install Fallon. But the move also has the potential to backfire with Leno's fans, who did not embrace new Tonight host Conan O'Brien when Leno was temporarily moved to prime time in 2009.

The first effort toward making a smooth transition came on Monday night, when Leno and Fallon appeared in a comic video making fun of all the late-night rumours with a spoof of West Side Story's Tonight. It aired in between each man's show.

Leno, in a statement, offered his congratulations to Fallon.

"I hope you're as lucky as me and hold on to the job until you're the old guy," he said. "If you need me, I'll be at the garage."

Fallon said, "I'm really excited to host a show that starts today instead of tomorrow."

US President Barack Obama, left, talks with Jay Leno during an ad break during a Tonight Show appearance in October. Picture: AP

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